He cares because eventually he will need Republican support on a myriad of other things, too. No president should operate as a dictator, period, not even Obama.
Maybe no President should operate as a dictator, but Obama has come the closest to operating as a dictator than we have seen in my lifetime. In my opinion he wants Republican support ONLY as a cover for the Democrats that his handlers are leading off the cliff like lemmings. He doesn't want to suffer the embarassment that the Clintons suffered in 1994. I say 'his handlers' because I no longer think that Obama is bright enough or competent enough to understand or even care about the extreme damage some of his policies would do to this country and its people.
I think his handlers do know but they will do it as the the only way they can wrest the USA away from the freedom loving people who helped forge it into the amazing nation that it is. Once they can destroy most of the mechanisms that have made it an amazing nation, and the government has power over every aspect of our lives, then they will have total power to mold it into whatever entity they want. And I don't think we're going to like what they want.